Overload circuit-breaking apparatus



E. 0. SCHWElTZE-R. OVERLOAD CIRCUIT BREAKING APPARATUS APPLICATION FILED OCT. I2. 19I8.

Reissued June 8, 1920. I

UNITED STATES PATENT" OFFI..CE.

EDMUND o. scnwmrznn, or cnrcaeo, rumors.

OVERLOAD CIRCUIT-BREAKING- arrmrus.

Specification of Reissued Letters Patent. Reigsfied-June 8, 1920;

Original K0. 1,211,967, dated January 9, 1917,Scr1al 170,768,577, filed Kay 1a, 1913. Lpplioaflon 1 1- reissue fled October .12. 1918. Serial No. 257.907.

To all whom it may concern Be it known that I, EDMUND O. bonwnrn zim, a citizen of the United States, and res i dent of Chicago, in the countyof Cook and State of- Illinois, have invented a new and Improved Overload Circuit-BreakingApparatus, of which the following" is a full, clear,

quickness and accuracy of operation; tot-- minimize the arcing and destructlve efi'ect when the circuit is broken; to insure reliability and certainty of operation; and to secure the fore oing and other desirable results in a simp eand expeditious manner.

The switching or interrupting of current flow on circuits 0 er'ating on high tension is in general a di cult and dangerous matter.- Whena line bears a heavy flow of current at a high voltage, physical separation of the conductors isfollowed by an are .which tendsto persist to a degree depending upon the resistance and inductance of the circuit, the capacity of the generating system back of it, and the voltage on, the

conductors. I

In practice previous to my invention, the only feasible way to switch such current flow was by oil switches, but oil switches are very expensive in costand upkeep and in large sizes are slow to operate.- Theuse of air break switches for such service has been.

wholly unpracticable heretofore The reason for this is thatthe arc which-is formed destroys the switch contact. Particularly upon a shorted or overloaded line an air I break switch is useless because. when the blade is. opened, the arc follows the full The provision of oil switches at various points on a line or system where it is desirable to have means for opening the circuit is not feasible, because "of first cost i and I further because of the inability to give them proper attention for maintenance.- As a result, most lines are inadequately provided with. circuit breakers.

The statements above made with respect to an air break switch also hold true of any type of swltch, the voltage interrupting capacity of which is below that of the -circuit upon which it is to be used, whether of air break switch, oil switch .or any other type. 1

According to my invention I provide a switch which,'of itself is incapable of satisfactorily'interrupting the-flow. of current at the voltage at which thelline is operated and a by means of afuse of special character in shunt with the switch I am able to take fromthe switch the actual duty of interrupting the current flow and place it upon the fuse carrying capacity.

In the accompanying drawings- Figure l is a diagrammatic view of high tension three phase power or lighting circuit-provided with overload circuit break ing apparatus'embodying m invention and Figs. 2 and 3are views of t e preferred and modified form of my apparatus, respectively. I

Inthe drawings I-have shown the line conductors 1, 2 and 3, representing the three high tension lines or conductors of a threephase system supplied by dynamo or. generator 4. The conductors 5, 6 and 7 are other line conductors leading oif from the. conductors 1, 2 and 3, the conductors 5, 6 and 7 being understood to run through some suitable transmission device or other apparatus requiring overload current protection. Each of the lines 5, '6 and 7 I show equipped with automatic overload circuit breaking apIparatus involving my present invention. show in connection with line or conductor 5, for example, the fuse 8 which is-of very low carrying capacity, preferably 'a very small percent., for-instance, one percent., of the entire carrying capacity or load carried by conductor 5.

I also show a circuitbreaker 9'Which may be any suitable or desirable type of automatic commercial circuit breaker preferably of the air break type. The contacts 10-10 of this circuit breaker are connected by wires 11 and 12 with they line 5"so that v breaker.

.suflicient overload passes in the line 5 the solenoid 14 -will actuate the circuit breaker 9 and thereby open the circuit across the 'contacts 1010, whereupon the entire current will'be thrown upon the fuse 8, thereby operating or .blowing said fuse instanta- 5. It will be seen that reliability, certainty neously, the fuse having-a relatively small carrying capacity. The other lines 6 and 7 I show also provided with; fuses 8+8 and circuit breakers 9- 9 connected and operating as described in connection with line and quickness of action are secured, the circuit breaker operating quickly when a t predetermined overload is reached and then the fuse operating. Thus, with a low voltage circuit breaker of small and cheap design and a low capacity fuse of high voltage, a very rapid operating mechanisnr is ob-' tained with reliability of action and low maintenance cost. same time that the arcing effect is taken care of by the character of the arrangement of circuit breaker and fuse, and protection for the translating apparatus on the line is thereby insured because the circuit breaker This insures against such first operation of =the circuit breaking mechanism at thegenwith its tripping coil in the primary circuit is .more responsive and will operate more quickly than theusual oil switch and tripping mechanismat the generating stations;

crating station, with consequent ill effects upon the service given other loads connected to the same circuit.

"When desired, the circuit breaker may be immersed in oil, although as -a general rule this is not'necessary because there is no a little arc. With the arrangement as shown in my invention, it is easy and inexpensive to replace the fuse since it is contained in a removable cartridge.

'In ig. 2 have shown the pre e ed It will be seen at the r a very much as the operation of the form of apparatus which I employ. This embodies a swinging knife blade switch 16 pivoted at 17 'to a post 18 secured to an upright support 19., The blade 16 has an extension 20 to which is secured a spring 21, also fastened to the support 19, said spring tending to draw said extension 20 toward the support 19. This upright support is made of insulation. Spring contact jaws 22 are also mounted upon the, upright support 19 and are arranged to coeperate with the blade 16 and other contact jaws 23 also mounted'on the support 19 are arranged to cooperate with the extension 20.

These contacts are suitably insulated from each other. An electromagnet or solenoid 24 is shown mounted upon the support 19, being conveniently associated with the jaws 22'and'is provided with an armature '25. This armature 25 is pivotally connected at its lower end to a support 26 and at its upper end constitutes a support for the links 27 and 28 which are pivotally connected to one another, by frictionally engaging the under sides of the links at their pivotal point to retain the links in the position disclosed in Fig. 2, it being. understood that the link 27 is in the form of a hook or catch to engage the end of the switch blade 16. A spring 29 acts upon the catch 27 tending to hold the same in engagement with the switch blade 16. Thus, the blade 16 is normally held closedin the contact 22 by the catch 27, but when the solenoid 24 is en'- ergi'zed and the armature 25 attracted, the catch 27' is shifted due to the action of the spring member 29 so as to disengage the blade 16, thereby permitting the spring 21 toactuate the same and separate the blade 16 from the contact 22 and cause extensions 20 to connect with the contact jaws 23, the links 27 and 28 having a loose connection withone another and with the armature 25 with suflicient loose motion to permit a;

'mounted a pair of posts 30-and 31 which support an in'closed fuse 32. The arrangev ment is so connected that the solenoid 24 is included in the circuit as shown in Fig. 1,

and when the solenoid is energized by an I overload current and the blade 16 released, the circuit through the blade 16 byway of contact jaws 22 is opened, and the fuse 32 is connected in shunt by the extension 20 meeting the spring jaws 23, the connection to the swinging blade 16 and extension 20 being by way of metal rods to posts 18.

Thus the operation of this arran ement is ig. 1 apparatus, the switch or circuit breaker being first opened and then a shunt through the fuse being 0 ened.

'In Fig, 3 have shown an arrangement very similar to that of Fig. 2, but instead of having three posts on the upright 19 I have shown in Fig. 3 only two posts, namely, the spring jaws 22 and the post 18 to which the switch blade 16 is pivoted. The fuse 32 is connected with the posts 30, as in Fig. 2, and also with the posts 31, being a rear extension of the post 18.. Thus a fuse 32 is normally connected in shunt with the circuit breaker or switch instead of being thrown into shunt by the operation of the switch as in Fig. 2.

It will be understood that changes and modifications may be made without departing from the spirit of the invention.

What I claim is:-

1. The combination of a circuit breaking device having a swinging knife blade, spring contact jaws therefor mounted upon an insulating support, electromagnetically controlled means tending to hold said knife blade normally in position in said contact jaws, spring means tending to open said knife blade, and a fuse mounted on'the opposite side of said support and arranged for connection in shunt between the spring contact jaws for said knife blade.

2. A circuit breaking device comprising a support, contact jaws carried by a metallic post which extends through said support and has its opposite end made in the form of a fuse terminal, a swinging blade adapted to engage said contact jaws and mounted upon a post also carried by said support on the same side thereof as said contact jaws, another post mounted on the other side of said support and providing the other fuse terminal on the same side of said support as said first mentioned terminal, amagnet and a trip device controlled by the armature thereof for controlling said blade.

3. A circuit breaking device comprising a support, contact jaws carried by a metallic post which extends through said support and has its opposite end made in the form of a fuse terminal, a swinging blade adapted to engage said contact jaws and mounted upon a post also carried by said support on the same side thereof as said contact jaws,

another post mounted on the other side of 60 said support and providing "the other fuse terminal on the same side of said support as said first mentioned terminal, a magnet and a trip device controlled by the armature thereof for controlling said blade, said second mentioned fuse terminal post being an 1 extension of the post upon which said swinging bladeis mounted.

.4. In combination, an air break switch having means for opening the same, a fusible element of small current carrying capacity compared to the normal load of the i switch, means for connecting the fusible element across the terminals of the switch when the switch is opened to receive and then break the flow of current, and a barrier of insulation between the fusible element and the switch to prevent mutual interaction between the fusible element and the switch.

5. Ina device for interrupting a. current flow at high voltage, a switch inherently unable to break the flow of current at full-load and at the desired voltage, and a fusible element in shunt with the switch, said fusible element being of a current conducting capacity comprising only a small percentage of the current carrying capacity of the switch, being of a voltage interrupting capacity in excess of the voltage impressed upon the switch and a barrier'of insulation between the fusible element and the, switch for preventing the arcing at the fuse from affecting the break at the switch.

6. In combination, a switch, a fuse and means for connecting the fuse across the terminals of the switch only after the switch 

